There is one inalienable truth about happiness. Grumpy old men, and women, are not grumpy whatsoever -- contrary to popular myth. In fact, this truth remains the most contrarian of all research on happiness, and, to the best of my knowledge, is still the most evidence-based.
Is it more important to have a contented love relationship or achieve your full potential? Which outcome will make you happiest... and does it have to be a choice?
Offer advice that has someone else's best interests at heart, not yours. In my experience, many young women give their girlfriends advice, particularly that which relates to the love life, and it reflects on their current situation rather than on their girlfriend's situation.